One example of a conventionally known fuel cell system (see Japanese Laid Open Patent Publication 2002-313396) provides a voltage detection device in at least one location in the vicinity of the hydrogen exit or in the vicinity of the air exit of the fuel cell that has the greatest tendency for reduction in cell voltage due to water blockage, and detects water blockage in the fuel cell by determining whether the cell voltage detected by the voltage detection device is lower than a predetermined voltage.